Lyophilization is a process by which the volatile components of a drug are removed in order to extend the shelf-life of the medication. Lyophilization may involve the rapid freezing of a material at a very low temperature followed by rapid dehydration. Solvents such as water are removed from the drug yielding a substance that is more stable and can be stored. Lyophilized drugs are generally stored in a glass vial or cartridge and covered by a rubber stopper or septum.
In order to administer the lyophilized drugs, the drug must generally be reconstituted. The reconstitution process usually involves adding a diluent such as sterile water to the lyophilized drug. A syringe is typically used to inject the diluent into the vial containing the lyophilized drug. The syringe may be pre-filled with the diluent or the user may first withdraw the diluent from a second vial or container into the syringe. After the diluent is added to the vial containing the lyophilized drugs, the contents are then mixed to form a therapeutic agent.
After complete mixing of the diluent and the lyophilized drug, the therapeutic agent may be aspirated back into the syringe. Generally, the same needle is used to withdraw the diluent into the vial and to aspirate the therapeutic agent into the syringe. In some systems, a separate, filtering needle is used to withdraw the therapeutic agent.
Once the therapeutic agent is in the syringe, the medication is administered to the patient. Usually the therapeutic agent is administered within a short time after reconstitution in order to ensure that the drug is not degraded by the solvent. The needle used during reconstitution is typically replaced with an administration needle. The administration needle usually will have a smaller diameter than the needle used during reconstitution to reduce tissue damage and pain to the patient during administration.
Most current systems for reconstitution expose the user to the risk of inadvertent needle sticks. In addition, current systems may not adequately prevent the possible reuse of the syringe. Because of these risks, a number of needle guards for syringes have been developed that are intended to prevent accidental needle sticks and/or inadvertent reuse of a syringe.
Accordingly, a syringe system that can be used for reconstitution and that would automatically activate a needle shield during or following administration of the therapeutic agent would be considered useful.